Conventionally, there is a crimping type coupling as a hose coupling for connecting a hose to an apparatus, as shown in FIG. 7. The coupling includes a cylindrical nipple 11 and a cylindrical socket 12 disposed radially outwardly thereof. Provided on the radially inner surface of the socket 12 in a predetermined interval along the longitudinal direction of the socket are circumferentially extending annular projections 13 with an equal height for gripping a hose.
As shown in FIG. 8, a hose 16 is attached in such a manner that the socket 12 is crimped from its radially outer side by a plurality of crimping claws 14 to press the socket 12 to be smaller in diameter, thereby securing between the nipple 11 and the crimped socket 12 one end 16a of the hose 16 which has been inserted therebetween.
The crimping type hose coupling described above can quickly and easily secure the hose 16 using the crimping claws 14 and is thus advantageous in hose attachment workability, allowing the attachment working cost to be inexpensive. Also, various shaped ferrules can be employed therefor, and furthermore, in securing a hose which has been assembled to an elbow type coupling, the arrangement of the hose angle can be easy.
When the socket 12 is crimped from the radially outer side by the crimping claws 14, however, some gaps S between the crimping claws 14 are produced, resulting in that portions 12a of the socket 12 corresponding to the gaps S can not be effectively crimped. The force that compresses the hose 11 against the nipple 16, and the sealing ability between the inner surface of the hose 16 and the nipple 11 in the areas of the portions 12a, is reduced. As a result, crimping type hose couplings are limited to use in a low pressure range.